Ex13x.=√4+B其中A>B>0求证lmxn=A A=A≤√A+B"≤√2A="√2A n=(1+h)=1+mn-1) h2+ n(n-1) hn≤ ≤G√mEx13 n n n xn = A + B 其中 A>B>0 求证 xn A n = → lim A A A B A A n n n n n n n n =  +  2 = 2 + − = + = + 2 2 ( 1) (1 ) 1 n n n h n n n h … 2 2 ( 1) hn n n −  1 2 −  n hn n n n n n n n n n 2 1 2 2 1 1 = + − + + −  